An equilateral triangle is one where all the sides are the same length and all the angles are 60 degrees. It is the same in height as it is in width.
If you look at this from a crochet perspective it means that the row number will be the same as the number of stitches in that row.
The fourth row will have four stitches. The tenth will have ten.
It also means that the height of your stitches needs to be as close to the width of your stitches as possible. The best way to achieve this is to work in single crochet.
A single crochet is when you insert your hook in the next stitch, yarn over, pull through the stitch so you have two loops on the hook, yarn over again and pull through both loops on the hook.
If you are working from the point of the triangle for every increase in height (row) you will need to increase the same in width (stitch)
The best place to put your increase is on the first stitch of the row you are working.
If you are working from the base then every row will need to decrease by one stitch at the beginning of every row.
I like working from the point. I find that it makes a neater triangle for me and it is far easier to fix if you get the wrong number of rows.
First Row: Cast on and Chain 2
You will have three loops in your chain including the cast on stitch. That third loop from the hook is the point of your triangle.
Second Row: SC in that third loop from the hook. Chain 1 to turn
The two chains and SC will be the second row with two stitches in it. So there is one chain for turning, one chain that will be the first stitch of the row and the SC that will be the second stitch in the row.
Third Row: 2 SC in first stitch, 1 SC in each stitch to end, Chain 1 to turn. (3 Stitches in row)
Turn, 2 SC in first stich, SC in each stitch to end, Chain 1 to turn (4 stitches in row)
Carry on increasing 1 SC in each row until your triangle reaches the desired size.