"I burst into tears every time I see my late Mother's picture."
"I cry a lot every time I see my late Mother's picture."
What is the difference between those two sentences?
Conceptually, there's not much difference at all.
However, the phrase burst into tears conveys the notion of a sudden outburst of crying. It's possible to cry a lot without bursting into tears. You could weep more gradually, sniffling, sobbing, and crying one tear at a time over an extended time span. For example, a chef might "cry a lot" while slicing onions, without ever "bursting into tears."
Bursting into tears is an expression that usually describes someone who breaks into sudden weeping after being overcome by a strong emotion, such as joy or grief.
It's also possible to burst into tears without crying a lot. For example, after a mining accident, the father of a rescued coal miner might "burst into tears" upon hearing the news of his son's rescue, but then quickly regain his composure and smile in a huge sigh of relief, hugging his neighbors and other supporters.
Crying is a form of coping with strong emotions where tears run from the eyes, the nose runs, and may be accompanied by sounds of crying out in disbelief, anguish, or sadness.
Some of the fans cried after losing to their rival.
To burst into tears is to initiate crying with a sudden explosive action of tears and a facial expression of disbelief. After the initial outburst, it can then lead to any one of different types of crying (answers OP's original question).
The children burst into tears when Santa didn't come.
There are various forms of crying in order of intensity
(these descriptions are only guidelines and subjective)
tearing is water coming from the eyes possibly without a runny nose
weeping is a more intense tearing with subdued sounds of sadness
sobbing is a more intense form of weeping and a runny nose
crying is what on would usually think of
tantrum (for children) involves a physical breakdown and possibly flailing on the floor
wailing is a full on display of anguish characterised by screams
Crying usually occurs with sadness but may occur in times of happiness which are then called
Tears of Joy
She cried when he proposed marriage
The beauty contestant burst into tears upon winning the pageant.
As J.R. says, bursting into tears is a sudden reaction. I've recalled a poem, An Ancient Gesture, that illustrates the usage of the expression nicely:
I thought, as I wiped my eyes on the corner of my apron:
Penelope did this too.
And more than once: you can't keep weaving all day
And undoing it all through the night;
Your arms get tired, and the back of your neck gets tight;
And along towards morning, when you think it will never be light,
And your husband has been gone, and you don't know where, for years,
Suddenly you burst into tears;
There is simply nothing else to do.
You see - there's the build-up of emotion, and then suddenly you burst into tears.
Compare:
She cried for hours.
*She burst into tears for hours.
Bursting into tears refers to the moment of starting to cry. But of course it could also be used metonymically to refer to the full act of crying.
Dave is such a cry-baby, he bursts into tears all the time.