The concept of Bitcoin is actually the same as the concept of money. What gives FIAT money value? You can not eat FIAT money. The FIAT in your bank account -y ou can not touch it It is not even there - mostly it is just numbers - banks are giving out 10 times more money than they acutally have... If we would all go and try to cash out our money from the banks they would go bankrupt in no time at all!
What is Bitcoin? As with FIAT money the value is given to it by the people. You can not touch it either. BUT - supply is limited - this makes it deflationary instead of inflationary(FIAT money can be printed on demand!!!)
Hope this helps to make this issue a bit clearer.