linux-image-amd64 is a generic metapackage, which depends on the specific default kernel package. In your particular case,
linux-image-amd64 probably depends on
linux-image-3.16-2-amd64. In general it suffices to install the generic metapackage. You could alternatively install the specific
linux-image-3.16-2-amd64 package, but in general it is better style to install the generic metapackage.
One specific advantage of installing the generic metapackage (and keeping it installed) is that it makes sure you always stay current on system upgrades. Otherwise, supposing you are upgrading from one Debian release to the next, or even from Debian stable to Debian testing, your kernel version will not automatically be upgraded, aside from minor Debian-specific upgrades for security reasons. However, if you have the generic metapackage installed, the latest kernel will be pulled in as a dependency.
Note however, that the kernel that was already installed, as a dependency of
linux-image-amd64 or otherwise, will not be removed. So you will need to periodically prune the list of obsolete kernel packages, including header packages.