An equation has an equal sign; an expression does not.
Terms are separated by plus or minus signs. A polynomial has more than one term. Hopefully you know the difference between a BIcycle and a TRIcycle.
The degree is what power the variable (the letter) is raised to.
The coefficient is the number before the letter.
2x3 - 7x2 + 14x - 654/75 is a polynomial expression.The second term is -7x2, which has a coefficient of -7 and a degree of 2.
Go.