INT, STR, AGI - What exactly do they mean IN-GAME?

[Skoal1]

Exact definition we obviously know, but it's been so long (not being an original dota player) that I'm hoping someone can explain exactly what they mean IN-GAME?

IE. Does INT only increase mana or does it also increase spell damage / skilled spell DMG?

Does STR only increase HP or does increased STR points have any other effect?

Thanks in advance! :P

[Milkshake1]

I believe it goes as follows:
Agi-Increases attack speed and armor
Int-Increases mana and mana regen
Str-Increases hp and hp regen

Whatever your primary attribute, it will increase damage as well

[Netukka]

Taken from a STR hero, the +1 damage part goes to primary stat...
http://img38.imageshack.us/img38/561/shot0028p.jpg

[Phineas]

In-game you can hover the mouse over the icon below your character portrait and see the info that Netukka posted.

[A`nub`is]

Primary Attribut defines where the +1 damage bonus is applied.