All you have done in the previous chapters was great! But what if we want to use some of the numbers/results in the future? How can we save them?

The answer is simple - you need to use variables. Variable is like local storage for a specific value in computer memory. If we want to use them in the future, we need to refer to them. Therefore we need to name them somehow.

There are multiple rules to follow while naming a variable. These are:
- variable's names can not start with a number or dot followed by a number;
- variable's names can not have a `%` sign;
- variable's names can not start with underline `_` ;
- variable's names can start with a dot only if not followed by a number;
Note that these rules are not universal for all programming languages.

A good practice is to invest a particular meaning into a variable's name. For example, if you have the value `2020` representing a year, there is more sense in naming such a variable as `year`, `yr`, but not as `a`, `b` or something like that. This is not compulsory but recommended - this will ease the readability of your code for both yourself and other people.

To assign a value to a variable, use the `=` sign right to the variable name and left to value. For example, to assign `2020` to the variable `year`, we can use `year = 2020`.

In the first section, you will consider the very basics of R - outputting and performing basic operations. You will finish the section with the variables theory.

In the second section, you will learn the vector class in R, which represents single values too. You will consider the main data types for single values and how to work with multiple values of a kind at once.

Factors (or categorical variables) are widely used in real life. These are blood types, currencies, nationalities, brands, etc. Unlike numerical variables, factors are limited to a finite number of values.