I never saw this word "shears", but I found it on the internet and I went to search the meaning of that. Well, if scissors and shears have the same meaning. Let me know how to use each one.
The technical distinctions the other answers are giving might be true, but for the purpose of an English language learner, I think the most important distinction is that scissors is a very widely used term, and shears is a more specific, more technical term.
In other words, most people are going to call anything with two pivoting blades "scissors", it is only within certain professions/hobbies (hair styling, sewing, crafting), that they bother to distinguish between different types of scissors, shears, or snips.
In sewing, for example, you might have specialized scissors like crafting scissors, pinking shears, embroidery snips, dress-making shears, or tailor's scissors.
Scissors and shears are essentially the same type of object - that of two sharp opposing blades with some sort of hinge mechanism.
It's important to note that the holes are not necessarily the same size or shape. This depends on the ergonomic design of the scissors.
You can get left hand and right handed scissors where the blades are arranged so that you can see the surface of what you are cutting on top of the 'inner' cutting edge. (sometimes also with grooved holes to make holding them more comfortable)
Usually (there are probably exceptions the holes are for thumb and one finger (eg for nail scissors), others can have a thumb hold and a longer loop for all four fingers opposite (paper scissors), and some have long loops on both handles so they can be operated either way round.
You would grip each handle with a whole hand
Not a hard and fast rule!
There are obviously some exceptions here - particular sheep shears, which are hand held (among many other examples)
Sometimes the terms are used interchangeably - particularly I've heard kitchen scissors also being called kitchen shears
Also note: I am quoting a UK dictionary, so there is probably some variation in location here too.
Edit: Although I have just had a thought that maybe it's the cutting angle? Scissors cut through something (paper, card, the end/middle of hair, Shears to cut something perpendicular to a surface (so to cut wool away from a sheep's skin, to shear your hair close to your head)?
(1) At least here in the UK this seems to be the case - mileage may vary
shear noun Definition of shear (Entry 2 of 2) 1a(1): a cutting implement similar or identical to a pair of scissors but typically larger —usually used in plural (2): one blade of a pair of shears b: any of various cutting tools or machines operating by the action of opposed cutting edges of metal —usually used in plural
Please see the pictures below.
In non-technical terms, shears are usually for cutting hedges or bushes or plants and require two hands when used and they look like this:
And scissors are like this and are used with one hand:
"Scissors" is more likely used when the blades are long compared to the handles, and are used to cut through thin things, like paper. (Long blades relative to handle mean more cutting distance.)
"Shears" is more likely used when the handles are long compared to the blades, and are used to cut through thicker things, like cardboard or branches. (Short blades relative to handle mean more cutting force.)
If I were explaining the difference between scissors and shears to someone who was oblivious to the concept at all, I would say all scissors are shears but not all shears are scissors.
Let me elaborate, physical scissors and the word scissors is a less precise, less complicated version of shears, even in the most novice of cutting experienced persons. Now, shears are any two sharpened objects and smoothed on contacting sides, that ultimately cut something using some sort of pressure for example, physiologic, electrical, hydraulic, etc. Usually cutting things such as: cloth, plastic, metal, wood, etc.
In addition, most pivoting shears(scissors) are self sharpening(so please don't try to sharpen scissors or shears, unless you are a trained professional). Whereas hydraulic and pneumatic shears must be sharpened and/or replaced quite often if they are shearing hard materials with acute accuracy, like metal.
The best example of my premise would be used in a vernacular:
The cliff was a shear drop all the way to the bottom.
The shear encounter with the burglar left her traumatized.
The new cloth that the seamstress ordered wasn't even shear to the touch, so she immediately sent it back.
In laymen terms scissors are a specific type of shears. Whereas shears have many terminological variations for its meaning, i.e. precise, close, accurate, acute, etc.
I hope this summarizes what I believe everyone is trying to say in each response, only in tidbits. I hope this puts it together in a more understandable way. I welcome all questions, comments and criticism (positive or negative), just be respectful.