Definition of deep learning
Deep learning is a type of Machine learning that tries to mimic the way humans learn by using somethings called artificial neural networks(ANN) which basically resembles the human brain.
If you are having a little experience with machine learning, you might remember different kinds of model used for different purposes. Like linear regression, polynomial regression, k-means clustering etc. Well neural nets are one of them, and you can imagine deep learning as a whole new study about these neural nets, making it a subdomain of machine learning.
Applications of deep learning.
Deep learning has spread a lot in recent years. One of the most prominent example is object detection- computer being able to detect and classify things they see. This has also let to one of the most trending technology today, self driving cars. Not only this, they can do other simpler tasks too.
The special thing about deep learning and ANNs is that they are capable of doing all other things that other models can do. they can do things like linear regression, polynomial regression in more advanced way too.