I am assuming that you are asking ‘what is the meaning of science’?
The word science comes from Latin Scientia. The verb ‘scire’ means ‘to know’, therefore the word ‘scientia’, from which science is derived, means knowledge.
Science is the sytematic study of the natural and physical world through observation and experimentation. While there are many different branches of science nowadays, such as Biology, Chemistry, Physics, Astronomy, Biophysics, Geology, and and and… the scientific method is very similar.
When observing something (a rainbow, an electric discharge, a disease…) scientists try to explain what they have observed by formulating what is called a hypothesis. They then devise experiments by which they try to prove that their hypothesis is wrong. As long as they cannot prove that their hypothesis is invalid, it remains a possible explanation of what they have observed. If they or anyone else can show that the hypothesis is wrong, then you need to formulate a new hypothesis.
This means that on a daily basis, scientists try to prove that what they say is wrong: how crazy is that?
A hypothesis is different from a theory. While a hypothesis is temporary and will eventually be replaced by a new one, a theory is a hypothesis which has stood the test of time, so a hypothesis which no one has been able to disprove for many years, and therefore becomes part of what is generally accepted by all: theory of gravitation, theory of atomic structure, and yes, also the theory of evolution. So theory is the best we have in science. It is not absolute, and could be proven wrong one day, but it is very, very difficult to do so as there is so much evidence supporting it.