The reason behind "Basis Points" is that saying something has increased by a percentage is ambiguous.

If interest rates are 5% and they are "increased by 0.25%", does that make them 5.25% (adding 0.25% of 100) or 5.0125% (adding 0.25% of 5).

Basis points are supposed to be an unambiguous way of explaining the increase.

It is 1/100 of a percent [1]. Just a different way of saying .25%

[1] https://en.wikipedia.org/wiki/Basis_point

Aka bips