Gross salary is the pre-tax amount that is awarded to the employee. Taxes include social security contributions and/or other mandatory payments according to local laws, and income tax, which varies both according to local laws and the employee's personal tax situation.
Net salary is the post-tax amount that the employee actually receives in their bank account. The rules for calculating the net salary also vary from country to country according to their legal framework.
Remote can only provide estimates of the net salary before the first salary. Net salary will depend on mandatory taxes, social contributions, benefits offered to the employee and other deductions.