Suppose you need some raw material, for instance, to engineer an FSD module. In my case, this was Arsenic. According to EDDB the worlds highest in Arsenic are only 2.9% Arsenic, the stuff isn't exactly laying around to be scooped up. You could go to one of these Arsenic "rich" worlds, drive around randomly for hours in your SRV hoping to stumble across an outcrop, a mesosiderite or metallic meteorite and hoping again that those structures grudgingly give up 3 or six units of Arsenic OR, what if you could go to a place where you could be relatively sure to find some Arsenic?
Go to geological sites. Each site will likely have fumaroles, or geysers, or some structure with deposits containing the raw materials that planet has available attached to them. Each type of deposit gives up different materials but the drop is consistent so you must determine, through testing (prospecting) which deposits give up the materials you are looking for. The planet I was prospecting, Umbila 1 C a, in addition to Arsenic and Carbon (Crystal Fragments) was also giving up Yttrium (Needle Crystals), Tungsten and Mercury (Crystal Clusters), plus Iron, Sulfur and Phosphorus (Pisceos Cobbles). Once you have determined which type of deposit gives up the raw material you are looking for you can save time by ignoring the rest. In my case I was short on Carbon, Tungsten, Phosphorus and Iron too so Umbila 1 C a was a candy store with 20 something geological sites. Once one of the sites was cleaned out I just moved on to the next and am now full up on Arsenic, Yttrium, Carbon, Selenium, Mercury, Tungsten, Iron, Phosphorus and Sulfur.
Not bad for a day's work. o7
PS: Whenver possible, land your ship right in the middle of the site. That way, your ship identifies several deposits for you before you even deploy the SRV.