What is polar

covalent bond is formed by sharing of electron pair btw two atoms of same or diff element .

if it is formed btw atom of diff element then atms involved will hv diff electronegativity values

so shared pair of electrom will b slightly displaced towards more electronegative atom giving it partially negative charge  n partial positive charge to the other involved atom .so giving polar character to covalent bond

C–H       C is partially negative n H is partialy positive  as C is more electronegative then H

polarity may also arise due to other reasons in a covalent bond as due to lone pair effect of O in water ,