It seems that we do three things all at once when we read and understand what we’ve read.
 

	We use our word knowledge (vocabulary).
	We process words quickly and accurately. This helps us construct mental representations about the text.
	We think about what we are reading to make inferences and check for inconsistencies. This is called meta-cognition.

The roots for reading comprehension start to grow in early childhood. For some young children this takes longer, and consequently, learning to read is not as easy for them. It is especially important that these young children get the extra help they need including: developing good vocabularies, acquiring a broad general knowledge base, learning the sounds of language, and acquiring strategies to help them think about what they are reading as they are reading it.

Check the Emergent Literacy Development Guide for appropriate language and literacy developmental milestones.