I just downloaded CentOS Minimal on my machine and installed it on my Oracle VM. While downloading I was confused which ISO to download. Because there are three kind od ISOs listed on download section of CentOS7 official Site https://www.centos.org/download. And there are no explanations on which ISO to prefer for which specific purposes. So I did a little internet surfing on google and CentOS community support forums and came up with this conclusion.
I'm going to prefer Minimal. The size of ISO is minimal i.e. 680 MB compared to DVD and Everything. So you can install is quickly and install less than 5 minutes. You can come live with a new OS and perform your CentOS operation for which you installed it. You can do a kickstart network install in short time.
But minimal won't be a good choice if this is your first encounter with Linux Based Operating Systems. And that you donot have adequate skills to play with Terminal. Because you won't get a Desktop Environment installed with Minimal ISO. And you will get only necessary packages which runs your operating system as well as some other basic components. Everything you want you should install it through terminal via YUM package manager.
I would recommend to choose either of the remaining two ISOs if you have enough time and want to get every packages in a single download.
Everything - apparently comes with all CentOS7 packages plus extra packages that are not automatically installed, but can be installed manually well after initial installation is complete. So if size is not a problem for you you can go with installation via Everything ISO.
DVD is also quite similar which contains also contains all packages in the iso and you select and install packages you want from the GUI installer. The "Everything" DVD is intended for people who will be setting up local mirrors so that that can just clone that and use it as a base. In Suppose you want full working application installed on your computer and you don't have internet access. So in tis case you choose DVD.