What's the difference between arithmetic, geometric, harmonic and Fabonacci sequences?

A sequence is called an arythmetic sequence if the difference of the term and the previous term is always the same.
For example, ${\displaystyle a_{n+1}-a_n=cons\tan t\left(d\right)}$
the constant difference, generally denoted by (d) is called the common difference.
Ex. ${\displaystyle 1,4,7,10,\dots }$ is an arythmetic sequence, whose first term is ${\displaystyle 1}$ and the common difference is equal to ${\displaystyle (4-1=3)}$
A sequence is called a geometric sequence if ${\displaystyle \frac{a_{n+1}}{a_n}=cons\tan t}$ for all n.
Ex. the sequence ${\displaystyle 4,12,36,\dots }$ is a geometric sequence, because ${\displaystyle \frac{12}{4}=\frac{36}{12}=\dots =3}$, which is constant.
A sequence is harmonic when each term is harmonic mean of the neighboring terms.
For example, ${\displaystyle \frac{1}{a},\frac{1}{a+d},\frac{1}{a+2d},\dots }$, here ${\displaystyle (a\ne 0)}$
Ex. ${\displaystyle 1,\frac{1}{2},\frac{1}{3},\frac{1}{4},\dots }$
here, ${\displaystyle a=1}$ (first term)
${\displaystyle d=1}$ (common difference)
The Fibonacci sequence starts like this: ${\displaystyle 0,1,1,2,3,5,8,13,21,\dots }$
Each number is the sum of the two numbers that precede it.

Arithmetic sequence is a sequence where the difference between two consecutive terms is constant while a geometric sequence is a sequence where the ratio between two consecutive terms is constant.