Create a "catalog" from a SharePoint list

Basically you'd need at least 2 SharePoint lists for this scenario. 1 list capturing all required hardware/software data and another 1 capturing users' requests. In the users' requests list you can use a column of type Lookup to the hardware/software list. This will render the dropdown that allows users to select the hardware or software item from the list. 

In defining your lookup column you can specify the column you'd like to see when selecting the item from the lookup list, typically this will be the title. In this case the title of the software or hardware item. You can also specify which other columns from the lookup list should be visible in the List View after saving an item with a lookup value. This way you could include your description. This description however won't be visible while adding a new Item.

As for the Description, you might need to do some form of customization to render the description right after selecting the hardware/software from the drop down. Traditionally this could be done with some JavaScript attached to the collumn using JSLink. JSLink functionality however is not available yet in modern lists so you might consider implementing your own "New item" experience for the requests list. This custom "New Item" experience could be implemented in many different ways...

Hope this helps!