I have a doubt about the use of these two pharal verbs: check on and check out.
So, can someone please give me some examples of uses?
For example:"Let's check out the traffic" or "Let's check on the traffic"

As with your examples, the two can be synonymous. The main difference is that 'check out' (in this sense) is casual English, while 'check on' is standard. As such, 'check out' can mean simply to view or join in some activity without any more analytic purpose.
Thank you Mister Micawber