Let's indicate an acid with HA.
Dissolved in water, HA can split off / donate H+.
In the same way we call the A- a base,
that - dissolved in water - can take up H+.
The following equilibria will be established:
HA + H2O H3O+ + A-
acid base acid base
A- is the geconjugated base of the acid HA
[water acts as a base]
A- + H2O HA + OH-
base acid acid base
HA the geconjugated acid of the base A-
[water acts as an acid]
An acid always turns into a base (and a base always becomes an acid).
If the difference between those two is not more than one proton (H+), such a couple is called a geconjugated pair.
Table I contains a table with acids and bases, in all cases accompanied by their conjugated partner.