Toddler may now set out on quests and missions for herself. She'll get a goal in her head such as "stack up all these blocks" and will become very determined to complete it no matter what. She'll be super happy if she manages it, and frustrated and teary if she doesn't. She probably won't appreciate any help, either, and will want to do it all on her own. It's probably best just to watch and let her get on with it - independence and problem solving are a great combination to develop.
Toddlers constantly learn new words and vocabulary from you, and you should be as descriptive as possible - not just a birdy but a noisy birdy, not just toast but brown toast, etcetera. The more descriptive you are, the faster and more advanced they will learn from you. Try to have conversations with them, as they try to talk back and will definitely appreciate you taking the time to listen to them, even if you have no idea what they're saying!