Hi Raggie and welcome to KH!
If you are knitting the chart in the round then you read the chart from left to right only...
If you are knitting back and forth every row then you will read most of the time the odd rows left to right and the even rows right to left.
Some charts do you use the same symbols but I have came across some where the designer chooses what the symbols will be...usually they give you a key.
Something else I will do with a chart is color code it...that way I don't have to keep looking at the key