Diffrences between oblique and italic

What is diffrences between oblique and italic?
Is italic version of the font is another font? What about oblique version of the font?
Oblique font is the same normal font that learn by browser?

Oblique means a slanted version of the original font. A true italic font is designed with different letter shapes - it is not just a slanted version of the same font.
Some sans-serif font families do not have a true italic font - just a slanted (oblique) version of the standard font.