Wow, a picture sure is worth a million words. In this wet basement photo we have a block wall filled with water. It has the typical signs including staining of the wall at the mortar joints, cracks with staining and moisture present. The homeowner has installed both a drain tile system and a cove drain system.
The drain tile system is high-end with a nice control panel for the pump and there's probably a battery back-up for the pump install in another room in case there's a power failure. The white PVC pipe is the sump pump discharge that goes out to the yard.
There's also a cove system installed at floor level. Several holes have been drilled into the cinder block cores at the floor level to relieve any water that fills the concrete blocks. Cracks in the outside wall have allowed water to build up in the blocks and the holes should provide an exit for the water which drains into the channel that leads to a sump pump.
Great Lakes Waterproofing was called in because this area was still getting wet and not a little wet but a lot wet, in fact a hole that someone had drilled into the block had a stream of water pouring out of it. Not only was the hole drilled 33" above the floor level but the blocks were full of water at this level. (a cinder block holds approximately 1.7 gallons of water)
The upper photo is roughly 7.5' wide by 4'+ tall, there's close to 51 gallons of water in this area of block, maybe more looking at the staining on the bottom course of white block. Imagine a typical city house with a footprint of 24' x 24', one wall could have hundreds of gallons of water in the blocks.
In this situation Great Lakes Waterproofing sealed the outside of the basement wall stopping the water before it filled the blocks truly waterproofing the basement
The cove system failed because rocks and debris clogged it up the water was unable to drain into the channel. The drain tile system failed for the same reason, the cracks on the outside wall were large enough to allow rocks and debris to fill up the first course of block, once filled both systems don't have a way drain the water. What options do you have when your water management system fail?