Crimp connectors are typically used to terminate stranded wire. A well-engineered and well-executed crimp is designed to be gas-tight, which prevents oxygen and moisture from reaching the metals (which are often different metals) and causing corrosion.
Wire crimping is typically a three step process that needs suitable connector and suitable crimping tool: In the first step of crimping, the terminal is inserted into the crimp tool. In the second step, the wire is inserted into the terminal. In the third step, the handles of the crimp tool are squeezed together, compressing and reshaping the terminal until it is cold-welded onto the wire.
Well done crimped connection is reliable, bit a crimped connection will only be reliable if a number of criteria are met. A wide variety of crimpers (a.k.a. crimp pliers) exist, and they are generally designed for a specific type and size of terminal. You need to pick the right tool and right connector for the given task to get good results.
Here is a collection of videos on connector crimping:
How to Use Wire Crimp Connectors
SN-28B Crimping tutorial for DuPont pins.
RC Tips: Crimping connectors (Dupont, Servo, Picoblade and Molex)
Tutorial: How to crimp connectors, strip wire and use heat shrink.
Crimping: Faston Connectors
Crimping: Molex Connectors
#230: How to install a BNC connector on RG-58 coax | DIY Repair
How to Crimp a BNC Connector & Make Your Own CCTV Cable.
How To Make RJ45 Network Patch Cables – Cat 5E and Cat 6