Vocabulary building skills are what children need to develop their growing vocabulary. Teachers typically encourage children to read widely and research. That's what building a vocabulary is - seeing a new word, researching what it means, and tucking it away to use later.
Basic and simple words are the first things that build up a child's vocabulary. These are tricky words, early reading words, adjectives, verbs or nouns. They typically only have a single meaning.
This tier is also sometimes called multiple meaning vocabulary tier, as the words within it can have more than one meaning. These words are also important for reading comprehension, used for direct instructions and may be descriptive.
These are words that are only used for a particular topic, so they may be called topic vocabulary. A child's low-frequency vocabulary might encompass topics like the weather or geography.
Vocabulary is important for speaking and communicating, but it's also essential for reading. It's the key to solid reading comprehension - it's impossible to read and understand a text if you don't know what the words mean!
When reading a text, we use our vocabulary knowledge to decode what the text is telling us. With a limited vocabulary, it'll be difficult to understand most of the words. This will restrict the overall understanding of the text.
Reading is also what helps to grow and expand a person's vocabulary. The more a person reads, the more vocabulary they'll know. But while a child is still growing their vocabulary, it's important that they're given a text at the right level - one where they'll understand most of the words, but there are some new ones to challenge and grow their vocabulary.