Linux – which directive in apache’s conf determines mime-type from file extension

Background :So in an attempt to learn apache, Im following along with the exercises in the book "Apache: The definitive guide". As part of these exercises, we're incrementally building up the httpd.conf file.

Problem: my html is getting served as plaintext. The mime-type is plain\text even though the file extension is .html

I'd like to know what directive i must add for it to pick up the right extension
Here's my conf file :

User webuser  
Group webgroup
ServerName my586
DocumentRoot /usr/www/APACHE3/site.first/htdocs
TransferLog logs/access_log
Listen 80

Additional Info to help diagnose the problem:

The exercise also mentions adding the following directive:
TypesConfig conf/mime.types

But this gives the following error:
Invalid command 'TypesConfig', perhaps misspelled or defined by a module not included in the server configuration
this led me to the believe it had something to d with the mod_mime module, but i havent been able to make it work through that either

Update: Interestingly, I presumed, images\jpegs would be shown as plain text too, but it shows them fine, i.e. sets the correct mime type on them.