I have not written General introductions for these CT pages.
The term Algebraic K-theory can mean a few different things. I think the database page will describe K-theory of schemes. There are various more general notions of Abstract K-theory; see Waldhausen K-theory, K-theory of categories, Quillen K-theory.
See K-theory for more clarification maybe.
Various variants of algebraic K-theory, and related notions:
K-theory with supports, Algebraic K-theory with compact supports, Homotopy invariant K-theory, Homotopy K-theory, Thomason-Trobaugh K-theory, Relative algebraic K-theory, <>ct:Bass K-theory>, Waldhausen A-theory
Algebraic G-theory, Topological G-theory?, G-theory, K'-theory
Barwick has written on K-theory of infinity-categories.
In increasing degree of obscurity
K-cohomology, Algebraic K-homology
Cohomology of commutative rings
There are many other kinds of K-theory, for these: do a search on World: KT (K-theory) (K-theory) (K-theory) (K-theory) (K-theory) (K-theory). We omit them for now. They include K-theory of stacks, and something with derivators.
nLab page on K20 K-theory (in algebraic geometry)