Like LoL, but a lot more unforgiving.
*Abilities don't scale with items, with the exception of a certain item increasing the damage on certain ultimates.
*There is no AD or AP as in LoL, just three attributes which give health/health regen, mana/mana regen, and attack speed/armor.
*Also there doesn't appear to be any sort of fixed metagame, unlike League with its standard bruiser top, caster mid, support/carry bot and jungler.
*Every hero uses mana as a resource.
*There is no combine cost for some items, but there are items called recipes which you must buy in order to complete certain items.
*CC is much more brutal, with fifteen second silences and five second stuns.
*You can control more than one unit, players control their own hero and a courier, and some heroes can summon units that they control. In League there's things like Tibbers, and Shaco clones, but to control those you can only hold alt and move the unit.
*Upon death, you lose gold. Killing a hero will not decrease their value. Bounties are pretty much the same thing, also exp reward from kills is much greater
*You can kill your own creeps when they are under 50% hp, only with autoattacks and certain skills, this is called denying and stops a hero from killing the creep for gold, while also decreasing the exp gain from the creep.
*Trees and elevation which can be used to advantage
*Day/Night system, some heroes get stronger during the night (and day?)
*A lot of mids gank, whereas in LoL mid normally doesn't gank/would gain more benefit from staying in lane
*LoL level cap is 18 and you can only level abilities, each ability can be levelled to 5. In Dota, level cap is 25, and you can add +2 to attributes as well as level abilities to 4 and ultimates to 3, not every hero only has 3 standard skills, also the hotkeys are different for each hero (however in Dota 2 the ability hotkeys are standard QWER with some heroes having more skills that extend to d and f)
*Certain heroes have more vision range than others.
*Wards last longer
*Neutral creeps do not give buffs, the equivalent to Baron drops an item which is the equivalent to Guardian Angel's passive, and also Cheese on third death
*Two runespots, runes are items that can be taken instantly, or bottled (with an item) to be used for later, runes can double damage, make two clones of your hero, (which take and deal less damage) stealth, increase movespeed, or regenerate hp and mana greatly
*Lane creeps give a lot more gold than in LoL
*Unit collision is more important
*Different types of shops, there's a unified base shop in Dota 2 but in Dota they were segmented, a secret shop in the jungle on both sides, and a sidelane shop
*To return to base you must either walk or purchase an item that allows you to teleport to allied structures, in other words, no global recall spell
*Towers deal less damage but fire faster, the last hit on a tower will reward extra gold, towers can be denied to the enemy team just as creeps can
*No runepages/summoner spells
*No bushes
and that's about it. I've played both games, switched to LoL for a long time and now I'm playing Dota 2. Some negligible things are that lane creeps are pretty damn big compared to hero units, and nomenclature of heroes isn't always standard. In LoL most heroes are called by name (Malzahar, the Prophet of the Void) whereas in Dota, you refer to a hero mostly by their occupation/title. Yurnero the Juggernaut, Krobelus the Death Prophet. Some exceptions like Zeus the Lord of Olympia or Rikimaru the Stealth Assassin.