Web development is a broad term, basically referring to the conversion of your web site from a dream to reality. There are various ways to get this done.
The easiest to implement is basic html, but it’s not always the easiest to maintain. The more pages you add to the site, the more pages have to be modified if you want to change something that appears across all pages, like the Menu! And the more pages you have to change, the more chance of making a mistake.
With a small amount of php knowledge you could put certain parts of the site into separate files, which means you only have one change to make, and it’s reflected across the entire site. BUT, in order to do this, you ideally need to set your pc up as a server (I do this with xampp) or you’ll have to make changes on the live site, and THAT’s not a good idea.
With a much larger amount of php knowledge you could create your own CMS (content management system), which is what large corporations do. The advantage to creating your own CMS is that you can make it do exactly what you want it to do (although the impossible takes a little longer, as the adage goes), and thereby have some control over site loading times. The CMS that are available need various degrees of expertise, and as they cater for all options, can sometimes be very cumbersome to load – not a good thing when living with an antiquated Internet connection.