I am new to crypto currency and I don't know the Bitcoin is legal or not plse help me
It depends on your country because there are countries where bitcoin is legal but there are also countries that are not legalized but they allow the community to use it as a means of payment and as an alternative source of income.
If it is illegal in your country, unfortunately, you can not use it freely because the authorities will arrest you.
It's not an alternative source of income because bitcoin is just a currency, or a payment system, what give you the income is your labor, the exact job your do or when you are trading and you are profitable. I only believe it as an alternative currency but not an alternative source of income.