A push strategy can either be damage based or sustain based. Damage based push strategies relies on the team’s ability to plow through enemy structures and decimate everyone in the team’s path. This can be done by heroes that grant AOE auras that help push lanes and take down towers (Drow’s Marksmanship Aura, Vengeful Spirit’s Vengeance Aura, Lycan’s Howl). This can also be done by heroes who can control neutral units (Chen and Enchantress) or those who can summon their own units (Invoker, Enigma, Lycan).
Sustain based push strategy relies on the heroes’ abilities and item builds that allow the push to last longer. If damage based pushes are blitz, sustain based pushes are more of sieges. This can be done by tanky front liners who can take tower damage (Timbersaw, Tidehunter) while being constantly healed by supports (Omniknight, Witch Doctor, Undying, Enchantress).
Push strategies are incredibly effective if the enemy team does not have good wave clearing skills or if their carry requires a lot of farm before they become a threat.