How does Level Adjustment work for player characters?

I’m a recent DM and one of my players wants to play with the Doppelganger race (+4 LA).

We’re planning to start a new level 10 campaign, and I would like to know how can I use the +4 Level Adjustment in this case.

I’ve read some articles about how LA works but I couldn’t understand how can I apply it on this case.

Does it means that at a Level 10 campaign, the Doppelganger will have 6 class levels and in order to achieve class level 7 he will need the same EXP that normal race would need to achieve lvl 11?