Demeter was the god of the seasons and her daughter was Persephone. Demeter and Persephone would always play on the fields in their garden. Persephone would make Demeter feel so happy so it would make her flowers and plants grow so high and beautiful.
One day Hades decides to take his guard dog, Cerberus out on a walk to the real world. The dog saw Persephone and he ran to her and she petted him. She starts to sing to the dog and Hades loves her voice and wants her to marry him.
Hades wanted Persephone to be his one so he kidnapped her and brought her down to his underground world. She was very sad because she missed her mother but she tried to stay strong because she knew she would never marry him.
Zues is Demeter's dad and once he noticed that persephone was gone and that his daughter was very sad he knew he had to do something. Zues sent Hermes down to the underground world to go work out a deal with Hades.
Hermes then went to Hades' underground world to work out a deal for him to get Persephone back for some time. When they finally came up with the deal nobody actually liked the deal but they had to go along with it because at least they got Persephone back for some time.
The deal was that for 6 months Persephone would have to stay with Hades ( Winter ) and the other 6 months she would be with Demeter ( summer ). When she was with hades her mom would be sad so she would not grow any crops like winter is but when she was with her mom her mom was happy so she grew crops like in summer. This myth explains the reasons for the seasons.