No sparge method
The no sparge method sounds exactly like the name suggests- it's an all grain method where you do not do any sparge. The main advantage of such a method is that you avoid any problems with astringency or tannins, which you can extract from the mash, especially if you are doing a long fly sparge. The major problem with not doing a fly sparge is that you will be leaving a very large amount of sugars in the mash which will not go into your boil and thus your beer. This will drop your efficiency incredibly and make it difficult to estimate beforehand what your target gravity should be. The drop is efficiency is the reason most brewers give for not doing this.