Around a toddler's second birthday, you might hear them saying loads more words as their vocabulary starts to grow, though they still understand a lot more than they can say. But between the ages of around two and five, the number of words they know absolutely rockets, and they'll start sticking them all together into sentences like 'we go to the park'.
All kids learn language at different rates and that's totally normal but there are lots of ways you can help.
You might think that having the TV on would help them pick up language more quickly, as they hear more and more words, but evidence has shown that what makes a real difference is having conversations with them. The more they get distracted by images on the tv, or we get distracted by our phones, the less we're really communicating.
Focus on face to face conversation and by the time they start school, they'll be understanding thousands of words, way more than you'd find in most books!