Information about plugins can easily be found on google or for a visual clue, google images.
I would also recommend searching for information for these plugins in chrome browser as a lot of the plugins are described on german forums. Then just right click on the page and translate to English.
Tsmedia and kodi are basically just 2 different types of media portals with a graphical front ends that enable you to watch iptv streams, movies, tv series, music streams etc. They can be very slow and flaky on enigma2 boxes as the boxes don't really have to power or memory to handle them. Also a lot of the links in them are either dead, die fast or blocked by UK internet providers. (you may need to set up a VPN to bypass the blocks) This results in lots of questions to the people who include them in their backup images. They can be be very good once you have set everything up properly and you will probably get better quality streams than the current SD channels available. (Especially useful for foreign sports channels and porn :) ) Personally you are better setting these up on a latptop or tablet rather than asking your sat box to do everything. Kodi, showcase, popcorn are a million times better on a laptop or tablet.
You access most plugins via Menu...plugins (or green button). Some plugins will also have to be setup before use, usually found in their own various settings menu. Some of these settings files you will have to hunt for.
Plugins I currently have intstalled.
Cacheflush - automatic cache flushing so your box doesn't run out of memory and crashes
E2Speedtest - for testing your interent speed. Useful if your picture is glitching
EMC(pre installed) - Enhanced Mover center for playing and organising your movies, recordings etc
OPenWebif(pre installed) - This is actually quite awesome. It like a big glorified remote control for your pc. It opens an interface on your computer via an ip address that then enables to control your box, view channels on your pc, view bouquets, edit bouquets, change channel on your tv etc. Pretty much anything you can do on your satbox can be also done on your pc and so much more but in a much more friendly interface. To access it, go to menu...information...network, to get your ip address. i.e 192.168.1.105. Then on your computer just type in
http://192.168.1.105:80 leaving the port as 80 and change the IP address to your own.
Picture Player(pre installed) - basically does what it says, enables you to view pictures/screengrabs/photos on your box (BMP,PNG,JPG,GIF)
Screengrabber or
shootyourscreensetup - this is just takes a snapshot of your computer screen. Good for showing errors or new skin graphics :). With these you need to setup a button on your remote that will trigger the screengrab. i.e mute button.
XMLTVImport - This is a plugin that brings in extra data for your EPG. Usually used in conjuction with the XMLTVimport-rytec plugin for the data. The source of your epg data can be changed via the xmltv settings. Some are short, some are full description, some don't show info for all the channels.
Autobouqetsmaker - this is an automatic channel bouquet maker (your channel/favourite lists) with built in channel scan. Must be configured to your area for use.
Other plugins than tend to come as default with a fresh image / backup image install
dvdplayer
epgsearch -
imbd - allows you to pull information from the internet movie database website for which ever movie/tv series you are watching
Optional plugins
TSpanel - this is basically an advanced plugin/menu manager. It Has built in softcams for your line, extra addons you can download, extra tools, easy menu structure to find certain settings etc etc. Can be great for noobs but can also cause lots of crashes on your box. Can also be conflicting with your existing softcam software for your line.
Extnumberzap - shows more options when inputting channel numbers on your remote, i.e picon, number, channel, bouquet etc. Can also be used to slow down the input of the numbers. So you don't have to type 3 numbers in 1 millisecond :)
For all the other plugins, google them, download them, see what they do. See if they are useful to your personal setup. If you don't like them, just delete them.