I have some spots on my skin

Now like I've stated in some posts I'm healthy and I've noticed last night that there was this spot on my arm. I don't know if I had it before, but I have fair skin and the spot looks like, i mean I don't know how to explain the color i think it's just a barely light brown. Is this some sort of pigment discoloration or age spot? And if so how do what things can I use to get rid of it?

Are you sure it's not a birthmark you never knew you had? Has your skin been exposed to sun a lot lately? Reason why I ask is because I actually have a birthmark right above my knee on my right leg, but it's not noticeable until my legs are exposed to sun for quite some time. It's weird. I never discovered it, and my parents never even knew I had it, until I was 9. I have another birthmark on my right wrist, but that's there all the time, sun or no sun.