Deformation theory is a way of understanding how things change shape without breaking or falling apart. Imagine you have a toy car made of a material like clay. If you push the toy car a little bit, it will change its shape but it won't break. This is called deformation.
In mathematics, deformation theory is a way of studying how shapes change in a more advanced way. Imagine you have a shape like a circle or a square. If you want to understand what happens when you deform the shape a little bit, you can use deformation theory.
Let's say you have a circle made of a flexible material like rubber. If you squeeze the circle a little bit, it will change shape and become an ellipse. Deformation theory is a way of understanding how the circle changes into an ellipse without breaking.
Deformation theory is used in many fields of mathematics, from algebraic geometry to topology. It helps mathematicians study the properties of shapes and understand how they change under different conditions. It's a pretty complicated topic, but it's really cool if you're interested in math!