What is it called if a polygon has matching sides?

Answer 1

Unfortunately, your question isn't accurate enough for us to know what you mean. From what I can tell, you may be referring to matching lengths or sides that face the same way. There are two primary types of polygon, irregular polygons and regular polygons.

Regular polygons have equal lengths all around and therefore (if this is the right case), they have 'matching sides'. However, if you're looking for sides that are facing the same way, these are called 'parallel lines' or 'parallel line segments' if the shape has two endpoints.

Regular polygons with an even amount of sides will have parallel sides. However, regular polygons with an odd number of sides do not, until you go into a very far off range (like 5001-gons). To the human eye, this would look like a circle. In practice, people would see that the tiny line segments could be parallel.
Except simple logic denotes that even though the line segments LOOK parallel, our eyes can't see bending at a microscopic scale. Therefore, we can assume that the line segments would NOT be parallel. If you tried extending the lines, it would eventually (after many miles) meet.

Irregular polygons are a completely different matter, though.
The definition for a polygon is a two dimensional shape with more than one side, due to the prefix poly-, and -gon meaning two dimensional.
-hedron would make it three dimensional.

Irregular polygons could be anything, as long as it is two dimensional.
The sides of these polygons could be any length, have any bearing in relation to another and have different interior and exterior angles.

I can conclude that regular polygons do have sides of equal length and have parallel sides when there are an even number of sides overall. At a massive-side scale, it can be hard to identify parallel lines in polygons, but simple theorems keep things in check. Irregular polygons could satisfy one point or the other or neither (since having both would result in a parallelogram or even a rhombus).