When evidence is circumstantial it means that the evidence is evidence that tends to prove a fact by proving other events or circumstances which afford a basis for a reasonable inference of the occurrence of the fact at issue.
It can be harder for someone to be convicted on circumstantial evidence but it's not impossible to convict someone on circumstantial evidence.
There have been thousands of people convicted and sentenced to years in prison based on circumstantial evidence alone.
So it's a myth that you cannot be convicted and sentenced on circumstantial evidence but it makes it harder to be convicted on that alone.
Circumstantial evidence is evidence that relies on an inference to connect it to a conclusion of fact such as a fingerprint at the scene of a crime.
By contrast, direct evidence supports the truth of an assertion directly i.e., without need for any additional evidence or inference.