Update README with project explanation

Author: mrroot5

.gitignore

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 # Pyre type checker
 .pyre/
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+
+# IDEs
+.idea
+.vscode

README.md

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-# python-teach-learn
-This is a repository to teach and learn Python
+# Python teach and learn
+
+This is a repository to teach and learn Python.
+
+If you are a teacher, you can use all the exercises on this repo for your own purpose:
+teach some concept, exams, etc.
+
+As a student take a look to the explanations below.
+
+## Requirements
+
+* Python >= 3.6.
+* Git installed.
+* A GitHub account.
+
+## Repo structure
+
+On master you only have a few files, every exercise is inside his own branch.
+
+Every branch has a name with index + what we learn.
+For example the first branch is `0_hello-world`.
+Also, we have modifications to the main exercise on a branch, example: `0.1_hello-someone`.
+This modifications add more complexity to the main problem like is usually done on [code katas](https://en.wikipedia.org/wiki/Kata#Outside_martial_arts).
+
+> Katas starts with a simple problem and will be more complicated on every step
+
+## Step by step guide
+
+If you fork this repo, never update the original branches because you could have conflicts in the future. Instead of that, create new branches.
+
+### Step 0: Read it
+
+Yes, this should be your first step, read this README and, of course, we start with 0 not 1.
+If you do not know why, we will see it in the future, be patient.
+
+### Step 1: Fork
+
+You should fork this repo and then start working with it.
+How? We will see a step by step guide with git commands.
+
+If you use another tool like GitHub Desktop take a look to their docs.
+
+![fork button](docs/images/fork-btn.jpg)
+
+### Step 2: Setup the upstream
+
+This step is required to have the latests updates from the main repo in your forked one.
+
+When you setup this you will be able to:
+
+1. Update the master branch of your forked repo.
+2. Get any new branch created from the main repo.
+
+#### Add upstream remote origin
+
+```shell
+git remote add upstream [email protected]:mrroot5/python-teach-learn.git
+```
+
+#### Update branches
+
+This could be done with the fetch button on GitHub:
+
+![fetch button](docs/images/fetch-upstream-btn.jpg)
+
+Or with a git command:
+
+```shell
+git pull upstream master
+```
+
+Simply change master for the branch you want.
+On GitHub you must change to a new branch to have the option to fetch it.
+
+#### Update list of branches
+
+I do not know if GitHub have an option to do this so, this is the command:
+
+```shell
+git fetch upstream
+```