Hey guys,
I'm feeling this can be a really dumb question but I'll try it any way.
I'm projecting something on my Arduino and I may be connecting to much things on it.
So my question is, it has a max voltage input right?
So.., I can't use it to power my laptop right (dumb example)?
I have a voltmeter; I'm using the 5V input; How can I know how many Volts I'm using?
Thank you and please do not judge 
I'm projecting something on my Arduino and I may be connecting to much things on it.
So my question is, it has a max voltage input right?
So.., I can't use it to power my laptop right (dumb example)?
Right. You can't power very much through the Arduino, but an Arduino can share a "big" 5V power supply with other things as long as everything has it's own connection to the power supply.
I have a voltmeter; I'm using the 5V input; How can I know how many Volts I'm using?
I guess you're using 5V. 
But there is also current (Amps or milliamps = the flow of electricity).
...Here in the U.S. we have 120VAC at the power outlets. That voltage is always there (assuming no associated wall-switch) but with nothing plugged-in no current flows. If we plug-in (and turn-on) a 100W lamp about 1 Amp of current flows. If we plug-in a hair drier we might get 12 or 15 Amps of current. If we plug-in a hair drier and a toaster at the same time we get too much current and we blow a circuit breaker.
Voltage, current, and resistance are related by [u]Ohm's Law[/u] (Current = Voltage / Resistance). Resistance is "the resistance to current flow".
Power (Watts) is calculated as Voltage x Current.
frankdart:
Thank you and please do not judge
Sure, I get it. However, there are better resources elsewhere on the internet than here, for learning the basics of electronics.
"I have a voltmeter; I'm using the 5V input; How can I know how many Volts I'm using?"
Lots of multimeter tutorials on youtube you might check out so you will have a good idea of what your volt meter is displaying.