BleepingComputer.com: Is SATA 3 GB/s the same as 300 MB/s

Some hard drive specs say 3 Gb/s and others say 300 Mb/s. But there are articles that say things like

"SATA II or SATA/3Gbs doubled the speed to 300 MB/s or about 3 GB/s."

Um. so they both mean the same thing? MB = Megabytes right? GB = Gigabytes? GB = 1,000 MB. Isn't 3,000 MB more than 300 MB?

This confuses me.

SATA is of course a serial interface and is specified in bits-per-second. SATA II specification is 3 Gb/s (3 Gigabits). With the encoding overhead, the actual data transfer rate achieved approximates to 300 MB/s (Megabytes).