He is standing out or outside.
Someone is shouting outside.
It is raining out or outside.
closed as off-topic by Em.♦, Glorfindel, JavaLatte, StoneyB, Nathan Tuggy Sep 13 '16 at 15:39
This question appears to be off-topic. The users who voted to close gave these specific reasons:
- "Basic questions on spelling, meaning or pronunciation are off-topic as they should be answered using a dictionary. See: Policy for questions that are entirely answerable with a dictionary" – StoneyB, Nathan Tuggy
- "This question should include more details than have been provided here. Please edit to add the research you have done in your efforts to answer the question, or provide more context. See: Details, Please." – Em., Glorfindel, JavaLatte
outside generally refers to not being in a building, cave, or other enclosed area. If you are outside generally you can see the sky (unless you are under a tree, bridge, or the like.) Out is more generic and just refers to not being in.
"the dog crawled out" means the dog came out of something, this could be a house, a room, from under the bed, etc. "the dog crawled outside" specifically refers to the dog leaving a building (or other such thing). Or, if the dog is already not inside of a building(etc.), then outside is the location that the dog is crawling, basically it is crawling outside of buildings where it can see the sky.
I hope that made sense, it is somewhat hard to describe.
"outside" is a location relative to where you are (presumably, you are inside), so in all three of your samples, 'outside' is the normal choice.
"out" is usually directional, So your 'It is raining out' would be probably understood as it is raining inside but some of it is leaking through the walls / windows to the outside world (this is far less likely to happen in practice than 'It is raining in').
A less common use of "out" would be as a comparator; as in "He stood out from the crowd", meaning he was different from the rest of the people even if physically located amongst them.