Language refers to your child's ability to use language and understand language so that they can effectively communicate.
While every child develops differently, typically by the age of four your child will be able to understand the difference between he and she so they'll be able to also tell you stories about the girls and the boys and their class or their friends, and they're now also very into singing songs that they know like the Itsy Bitsy Spider, The Wheels on the Bus.
This is really a fun age where they're now speaking in sentences between five to six words long and they're telling you things which is always fun to hear. So encourage them to continue to tell you stories by asking them questions and by providing them opportunities where they can talk to you.
So for example, if you're reading them a story maybe stop at the end and have them tell you the ending of the story and if you're singing a song have them sing the end of the song to you, too. This is really a great engaging and interactive way to connect with your child and have fun with them.