The first is VirtualBox. Since you are not using it for commercial purposes, you may download and install the full-featured version for your host operating system. If you are a MS Windows user curious about Linux, this is ideal for you. If you are a Linux user curious about different distros, this works as well.
After you install VirtualBox on your host operating system, you need to learn how to use it. the VirtualBox site has excellent documentation. My suggestion for configuration are give the virtual machine the maximum amnount of RAM and video memory that is practical and set the network choice to "bridged" rather than "NAT".
Next stop is to download the NetbootCD. This CD contaions enough of an OS to enable wired Ethernet connectivity and download and install several Linux distros via FTP.
What can you install?
Now you can create a virtual machine for each distro and experiment to your heart's content. This is much safer and easier to implement that dual- or multi-booting.
Remember that when using VirtualBox, you are only exposing the virtual hardware to Linux, not the real hardware of your machine, so learn how to identify your real hardware and learn how to use Google to determine the level of Linux support for it.
One last suggestion. When you do decide to install a Linux distro on your machine "for real", save yourself some headaches and obtain a second hard drive for your Linux install. If your hardware permits booting from an external USB drive and the distro you have chosen permits installing on a USB drive, you are home free. Otherwise, you'll need to install the second drive as a temporary replacement to get Linux installed. Then you can move it to an external USB enclosure .
If your BIOS does not permit booting from an external USB drive, you might find plpbt4win to be useful. It is a special bootloader that can boot an OS from an external USB drive. There are Linux and Windows versions.