A lot can be used to modify a noun, meaning a large
amount or number of people or things.
For
example:
"I
need a lot of time to develop this web site."
It can
also be used as an adverb, meaning very much or very often.
For
example:
"I
look a lot like my sister."
It has
become a common term in speech; and is increasingly used in writing.
Alot does not exist! There is no such word in the English language. If
you write it this way - imagine me shouting at you - "No Such Word!"
Allot is a verb, which means to give (especially a
share of something) for a particular purpose.
For example: "We were allotted a desk each."