How are those connectors called?
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It is a widely-used 4-pin female connector, a crimp housing with four female crimp terminals inserted. There are many manufacturers that make a connector like this, but Molex makes one Part Number: 50-57-9004 (SL™ Crimp Housing, Single Row, Version A, Non-polarized, 4 Circuits) in the SL Modular connector line. You can order this housing on Digi-Key.
You can easily crimp these terminals yourself with a low cost hand crimping tool if you want to make cable assemblies with this kind of connector. You'd need to buy a bag of female crimp terminals to use, then after crimping the wires, you insert the terminals into place in the housing.
You'll find that Molex manufactures these connectors, part of their SL line - non-polarized housing, in particular. In my experience, however, they're far more commonly termed "DuPont connectors". (People more often relate latched connectors to Molex.) They are also colloquially referred to as "jumper connectors" or "pin header connectors" on occasion, which is a bit vague, but since 0.1" pitch is most common, the terms are more often than not in allusion to these guys.
Edit: Almost forgot, the proper name, I believe is "Mini-PV", originally produced by DuPont, hence "DuPont connector", even though they made others.