There are several large and separate areas of evidence that all complement each other.
The first one recognized was that all life can be sorted into an order that links many similar forms together into small groups, and those groups into larger but a bit less similar groups, etc. For instance, all the different varieties of dogs, wolves and foxes are a lot more similar in their construction details than any of them are to any other kinds of animals. Same with cats, lions tigers, bobcats, etc. But those two groups are similar to lots of other groups of four legged animals that bear live young (do not lay eggs), feed their young with milk, have fur and all have very similar skeletal structures. We call this larger group mammals. But all mammals also have lots of more basic structural similarities with other egg laying, four legged animals like crocodiles and lizards. Each of the grouping levels indicates relatedness, but as the groupings get larger, there is less similarities in the details. This sorting scheme is completely consistent with all these animals being part of a historic family tree, with more similar examples sharing a common ancestor more recently and less similar examples having been changing longer since they last shared a common ancestor. This evidence was available long before Darwin, waiting for someone to realize what it meant.
Then there is the developmental evidence. As animals build themselves from a single fertilized egg, they go through a very similar sequence of developmental changes, with most of the big differences taking place late in the sequence. A one week old chicken embryo looks a lot like a one week old horse embryo or a one week old human embryo. This evidence is consistent with animals evolving into different forms by changes (mutations) in the building plan that they use to construct themselves.
There is fossil evidence that allows us to order, in time, the appearance of different forms. This fossil sequence very accurately mirrors the relatedness and common ancestry that shows up in the groupings based on physical similarity. It helps define what the last common ancestors looked like for any pair of modern forms you want to compare and adds independent timing details to the process. This is where the entirely separate geochemical radioisotope rock dating puts real age data onto the sequences.
The most recent category of evidence is our ability to sequence DNA from living things or recently dead remains to see how they are similar and how they are different. And guess what? The DNA similarities track in parallel to the structural similarities if the parts of the DNA that produces proteins or enzymes. But it turns out that most DNA in any life form is just a lot of junk that does not do any thing very important or maybe, anything at all. It just goes along for the ride. So mutations in that junk do not cause any noticeable changes in the life forms, positive or negative. So they are not discarded or amplified, depending on the reproductive success of individuals. This makes them a sort of clock (assuming that mutations happen randomly, whether the DNA is used or junk. So the more differences there are in the junk DNA that two forms share, the longer it has been since they shared a common ancestor. And... wait for it... this timing scale closely tracks the estimates based on physical traits and that provided by fossil evidence.
So all these different categories of evidence all reinforce each other to confirm the likeliness of the validity of the theory of evolution. There is no evidence available that does not fit into the explanation of the theory.
The theory of evolution is now, because of all the confirming evidence, the foundation of all medical and biological science and the basis of a billion dollar a year industry that artificially evolves life forms to order.
I hope this addresses your question.