What is the difference between natural selection and adaptation?
Natural Selection

Natural selection is the differential in survival and/or reproductive success among different individuals. As such, natural selection also refers to the process by which genotypes associated with greater fitness increase in frequency in the population through time.

More information on wikipedia > Natural Selection

Adaptation

An adaptation (or an adaptive trait) is a trait with a functional role that evolved (and is maintained) by means of natural selection.

More information on wikipedia > adaptation

Usage

Both the terms adaptation and natural selection are extensively used in science (and none of them come from the creationist religious belief). Their definitions are related as one is causing the other but these terms are not synonyms.

Further information

As the question is very introductory in the field of evolutionary biology, you might want to have a look at an introductory course to evolutionary biology. Evolution 101 (a.k.a. Understanding Evolution) by UC Berkeley is short, concise and very accessible even for those that have little a priori knowledge in biology.

Side Note

You said "believe in evolution". It is of course a common phrasing from the creationist ideology. Evolution is a theory (a theory is very different from a hypothesis see this answer for more information) and therefore, the phrasing "to believe in evolution" sounds quite wrong as it wrongfully suggests evolution is a thing on which we could legitimately have different opinion about its existence.