Im looking for a "board" which i can hook sensors, and these readings can be passed on a computer via a USB, or from the computer can make a request for a reading from one of the sensors.
Im new, can you point out which product will do the job? This will be a help for me to begin with.
Thank you.
What sort of sensors?
Any Arduino board can do what you have described in general terms. However, the Devil is in the detail
What do you want to sense and have you got any sensors in mind ?
Pro Mini.
Altimeter, gps, compass, temperature, speed
Well with a wired connection, you can pick almost any Arduino with that discription I think
Altimeter, gps, compass, temperature, speed. I want to make maybe an automated foam-made airplane. Don't ask why i don't buy one, i like it as a hobby to experiment and make one.
I'd go for an Uno or a Mega for a first board. The mega costs a bit more but it has a lot more capabilities.
I think a 5V logic board like this is the way to go for a new user.
I think you are right. I would suggest to get one with a DIP form processor, not SMD. It's cheaper when you break the cpu...
heavy to put in a foam-made airplane... depends on motor capability and size
Indeed, I missed his comment as I was typing mine.
My mistake
The #nano-family:nano-33-ble-sense has a number of built-in sensors and Bluetooth Low Energy so you can communicate readings without wires. It'll get you started fast so you can concentrate on programming instead of wiring... unless that's your thing. 
Perhaps starting with a pin budget would guide you in the right direction.
I would start making a list of the sensors you want to use and how you would need to communicate with them. Do they use SPI, I2C, discrete pins, a UART channel.
I2C devices all share the same 2 pins, whereas SPI devices share 3 pins + a 4th unique pin per device.
Do you need several UART channels - if you do, then that can eliminate a few boards straight away.
What voltages do these sensors operate at. Are they all 3.3V logic, or 5V logic or a mixture of the 2 ?
I see on this link (Mega) https://store.arduino.cc/usa/mega-2560-r3
Maybe this is not ideal, but very helpful. So in each pin of that opens, i can connect a sensor? And as i understood adruino can power up from the usb cable or with a battery alternatively. Correct? And also, how i can get from a single usb, multiple readings? If you have in mind any related link from this forum or a guide will be very helpful!
And more... can i attach little dc motors to power up from adruino?
Ah! Mission creep.(sp."Arduino")
No, you can't power DC motors directly.
It's likely that some of your sensors will be I2C devices, so will all be on a single pair of pins.
I have no idea for any of these details, but by pointing i will keep in mind to look for compatibility. Very useful.
Great detail, as you and somebody else mentioned. I will keep that in mind.
I'm just starting and with all these very useful replies, and fast (like the old irc days haha) in fact i might have already get a basic understanding, not just in adruino, but in sensor type devices, in general some basic concept of how this works. At least in the part of programing there'll be no issue.
You should wait until this thread develops a bit to buy. It sounds like you need two.
One Mega for making stuff on your bench and a much smaller lighter one for the plane. I would suggest research into other Arduinos used for flight along with what users recommend here.
DUE costs as much as Mega but way way better and more powerful board in the same form factor, why people bother with Mega beats me.
Maybe it's the 5V compatibility.