|Lesson:||LingQ 101, Getting Started|
"a lot" -- Something that you do very often, or that you do very much of.
"lot" -- A section of ground that you put a house or building on.
"lot" -- A grouping of things, sometimes sold at auction.
In this case, "a lot" is a phrase and has the first meaning. If you "read a lot" then you read very often.