This is kind of a more advanced concept.
Electron donating groups (EDG) and electron withdrawing groups (EWG) often modify acid and base strength, but are not themselves acids or bases. They also can stabilize or destabilize an acid or base depending on the charge of the conjugate created.
For example,
https://ibb.co/NChSRgS.
I often like to tie it in with Coloumb's law for physics, it's a pretty similar concept.
(+) charge generated from an EWG can stabilize (-) charge on a conjugate base, but (+) charge generated from an EWG can destabilize (+) charge on a conjugate acid. This can change depending on what your acids and bases are, as some conjugate acids and bases are neutral, so you can have opposite effects too.
Please let me know if this is unclear.