Q: What is the difference between ‘all’ and ‘every’? They have a similar meaning (I think) but we say ‘all people’ but ‘every person’. (Sasha from Russia)

A: Thanks for your question Sasha, let’s see if we can explain.

All and every can both be used to talk about people or things in general, or about all the members of a group. There is little difference in meaning, but every often suggests ‘without exception’. There is, however, a difference in the structures that are used with these words.

Every is used with singular nouns, to give the same meaning all is used with plural nouns.
Examples = Every child needs love
All children need love

We use all (of) with certain determiners (articles, possessives and demonstratives), but NOT every.
Examples = All of my friends bought me a present (NOT Every of my friend)
All the plates were broken (NOT Every the plate)

We use all with uncountable nouns
Example = I like all music (NOT I like every music)

When we talk about all day and every day we mean something DIFFERENT
Examples = I was here all day (from morning to night)
I was here every day (Monday, Tuesday, Wednesday etc)

So, the key things to remember are:
Use every with singular, countable nouns
Use all with plural nouns and uncountable nouns 
Use all with ‘of my/your’, ‘this/that’
All day refers to ONE day, from the beginning to the end
Every day refers to a sequence, one day, then the next, then the next

I hope this answers your question.