The first thing that children start doing Maths is when they learn to count. This happens with the objects they play or see. When parents say the numbers loud, children realize that they can use words to count. Starting from one, two, three, they start saying that while also connecting the words with the number of objects. It starts with the numbers 1, 2 and 3 and then slowly moves onto 4, 5 and numbers uptil 10.
The first models of numbers are the fingers. Given that we have ten fingers, children start learning to show numbers through the number of fingers. They learn that one finger is one, two fingers is two and so on uptil ten.
Next, they start to write the numbers in numeral form. They understand the way to write each number, and get a good idea of numerals just like they get to know about the alphabets.
After this, they start learning to write numbers in word form such as one, two, three etc. uptil ten.
As they grow, they start to learn reciting the numbers from 1 until 100. Once they learn from one to twenty, they begin to use them to count until 100 and more as well.
Slowly, they start to learn addition through learning that 1 plus two is three. The fingers become a model for their learning. But, before they start using the fingers, they orally learn to recite one plus two is three. Or, two plus two is four.
They start to be able to identify which number comes after a number. For example, they learn that eight comes after seven, four comes after three and so on.
Finally, they are able to count objects and say the number out loud. They realize that the last number they say when they count a set of objects is the number of the objects. They have reached the first level of mathematical competency.