What is this component and what is it used for?

10 ohm +/-5% wirewound resistor (probably inductive, perhaps fusible but it's hard to tell). Called a "cement" resistor. Made by KOA (Nagano, Japan-based company). If it's 13mm long, then 1W rating. J is the JIS or EIAJ standard code for +/-5% tolerance.

Here is a datasheet.

That's a 10Ohm fusible cement resistor with a 5% tolerance --->(J).

It's a 10 ohm resistor hence the label on the PCB called "R1".

The "J" stands for 5%.

what is it used for?

It's a power resistor and may be used for many things so I would urge you to read Wikipedia's page on resistors and hopefully it might enlighten you given that you have the device in your hand whilst all I have is a picture of it.