how LA works?

[Kerilstrasz]

So... lets assume a player wants to create a Pixie PC...
by MM1
A pixie character exchanges its 1 HD of fey for its first class level,
so a 1st-level pixie sorcerer has a d4 Hit Die, a +0 base attack bonus,
the base save bonuses of a sorcerer, and the sorcerer’s skill points
and class skills.
Level adjustment +4
so... a Pixie Sorcerer lvl1 is fit with a group of PCs lvl4? (LA +4)
or with PCs lvl 5? [LvL1 Sorcerer +4 (by LA)]

[Telonius]

Group of PCs level 5. The standard PHB races are LA+0. A race with LA+1 (and no racial hitdice) fits in with Level 2 PCs, LA+2 with Level 3 PCs and so on.

[Lostbutseeking]

One class level plus 4 LA = ECL 5.

[Urpriest]

ECL 5 as everyone is saying. All this and more explained in my Monster Handbook, link in sig.