lot

[Abdul munam]

when i can use a lot and many

[engee30]

when i can use a lot and many

A lot of is normally used in affirmative sentences; many in negative and interrogative sentences.

There are a lot of children in our school.
There aren't many apples on that tree.
Are there many dogs in the shelter?

Many is used with countable plural nouns only; a lot of with uncountable and plural ones.