Here are some examples:
Language development - talking to them, teaching them new words, listening to them. They may only be babies but their brains are like sponges and they are taking everything on board. That's why singing, reading and playing with them is so important from birth onwards.
Social development - the interaction that takes place between you and your baby helps to develop realationships with other people.
Listening skills - listening is important to be able to distingusih between sounds that make up the words that we use every day. It is really important that babies and children have quiet time with no back ground noise daily in order to develop these skills. Even ten minutes a day can help to make a difference.
Showing that we value what they have to say and by giving praise for achivements (even small ones), helps to develop their confidence, self esteem and their potential for further learning.