diff --git a/.gitignore b/.gitignore
index 64fe83a..06366aa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 env/
-build/
\ No newline at end of file
+build/
+*\#*
\ No newline at end of file
diff --git a/source/statistics/introduction.rst b/source/statistics/introduction.rst
index 28fb145..0d968fa 100644
--- a/source/statistics/introduction.rst
+++ b/source/statistics/introduction.rst
@@ -1,4 +1,13 @@
 Introduction
 ==================
 
-dd
+Metrics
+----------------
+
+* **Expected value/Espérance**: Noted :math:`\mathbb{E}[X]`, is a **theorical value**. For example, when playing coin
+  flipping, the expected value for getting heads or tails is 0.5.
+
+Variance
+^^^^^^^^^^^^^^
+
+Variance can be seen as the expected squared deviation from the mean of a random variable :math:`X`.