Grouping - Benefits and What It Means
In League there is many things that come into play like farming, warding, the amounts of BM'ing to give, but there is one that is a apart of as I call it, "The Pinnacle of Success or Do This Shit To WIn"
Grouping is a major thing to do in MOBAs in general like for instance you could be wanting to seige mid thanks to you Hiemerdinger going 4/0/2 in Mid, nice job Hiemer. The best way to group is make sure you have communications up and tell your team to 'Group Mid', Strength In Numbers can mean a lot in things and doing things like defending towers, teamfighting, or going to Earth Drake can mean the difference of Opening the Gates or Welcome Back To Bronze.
When is the best time?
The best time to group is to see who is ready to stop farming and do something together, if you Nasus has enough stacks, your Jungle Gragas, and your ADC Varus with Janna Support have enough items then it'd be the best time to group for something, just know that is a possibility because someone or two need to farm since of a disconnect or something. When grouping, find an objective to take because just grouping for no reason can make your maximum potential as a group of five can waste unneeded time then so take something like a tower or steal Baron.
When is the worst time?
If you have your bot lane up ahead by the inner turret since of snowballing is really frequent now in Season 7, calling them just to take mid Outer Tower when your bot lane is almost done with the bot lane tower is really redundant. Another bad time is to natural splitpushers like Udyr and Tryndamere, going into teamfights with a splitepusher by your side isn't worth it because people like Tryndamere has his own job, their lack of Crowd Control effects are better off split pushing or sneaking objects.
The exceptions to Grouping...
Grouping is good to take down towers faster then just having only one or two people focus it (Unless if your Tryndamere or Udyr), so having strength in numbers like I said is good and all, but what if an event happened like your team having a massive wave going to the enemy's mid inhibitor and your team is taking Dragon without you, take an objective to open more problems for the team like taking a turret. Its a lose - lose - lose for the enemy team, one loss because they have given up a turret and dragon to save their inhibitor, another one to go steal that great Dragon Buff but they loose the inhibitor and turret, and finally another loss if they loose if they save top lane out turret but the dragon and inhibitor is gone.
How to counter grouping...
Splitpushing, having someone like Udyr or Tryndamere just cleaving down a tower for fun is stressful for you team because splitpushing is applying pressure that your team is going at either have to loose a tower for a teamfight win. Grouping has its perks like your top laner having those heals he doesn't have to use pots for or taking an objective, it can also lead into things like having a lane or two open for splitpushing or minions coming without help.
There you go! It took a while and I hope this helps you on your guide, thank you!