Topology is the study of geometrical objects wherein the relationships between geometrical features is important, but not the actual numbers defining those geometries, like distances and angles.
For example, in 2D topology all triangles are the same, they are more worried about how a triangle is different from a square and a circle.
In 3D, all cylinders are the same, an egg and a sphere are the same. The dimensions are not important. A cyclinder always has three surfaces, two of them do not have a common edge. A sphere or an egg has only one surface.
A famous topological problem is the problem of colouring a map. A country is defined by a boundary, and countries share common parts of boundaries. If you want to colour countries such that no two countries next to each other have the same colour, how many colours do you need?
if you think about it, the property of being 'next to each' other, which is a relational thing, is important, not the actual shape or length or size of the countries/border.
Another example is if you have a railway network, then finding shortest oaths between stations that are not directly connected is another problem. The connections are more important, not the geographical distances between stations.
A lot and a LOT of topology gets applied in computer science. The field of networks is a topological area, and the internet is one huge network. Another network is the banking systems, the stock exhanges. All problems of what is connected to what and how to let information flow in shortest times.
Sometimes road networks are also chosen based on simple topology concepts.
A map does not need more than 3 colours to make sure no two countries next to each other are coloured the same. A topological result.
A lot of robotics involves solving topological problems. Usually advanced stuff hits up against topology, so its in high-tech. but not always.