Tactical("tactical" as in combat system where non-stat based tactics matter, not related to "overall" play strategy) combat refers to various techniques to transform RPG combat into form resembling a realistic combat event.
Though they add realism, they introduce complexity and reliance on skills not typical of rpg as genre.
1.Direction of attack to target creates a bonus/malus:
front,back,side,from above/below carry different attack modifiers. "Backstab" is a popular modifier.
2.Wounds: Wounded entities lose speed or stats(e.g. life drain),specific body parts could modify damage received.
3.Terrain modifiers: range bonuses for high ground, speed bonus/malus for terrain type, AoE spells works on differrent terrain differently.
4.Environment effects change gameplay: weather effects as modifier(e.g. rain vs fire spells, water spells vs cold,wind vs projectiles,etc).
5.Realistic projectiles: power decay with distance, gravity arcs,etc.
6.Friendly fire:(controversial for non-hardcore rpgs) projectiles and spells affect everything, including allies.
7.Lots of collisions: objects collision preventing long range attacks, e.g. trees with realistic hitboxes.
8.Dynamic environment: Collisions with objects may initiate events(such as trees falling due damage).

Dodging/Jumping/Rolling skills isn't considered tactical, but a basic element of Action-RPG gameplay(combat skills). Tactical movement without relying on skills and knowledge of terrain/location advantages to maximize character effect is tactical combat.(i.e. if "tactics" are built-in skills and not player decisions they are not "tactical combat" but just combat)