There are many terms nowadays: ELL (formerly called SLL = Second Language Learners), ESL = English as a Second Language), LEP = Limited English Proficiency, etc.
Here are some sites to try:
Personally, I like the following site to explain about language acquisition:
It's rather amazing that this year (2010) over 30% of the homes will have learners whose first language is NOT English.
As for a struggling reader, that could be a native English speaker (first language) simply trying to learn to read.