You can install RAM from a different manufacturer, as long as the specifications are the same.
For example, when your computer currently has a DDR3 SO-DIMM module with a speed of 1600MHz installed, you should only use DDR3 SO-DIMMs with a 1600 MHz speed to upgrade/replace your RAM. It is possible to use different frequencies but the system will then use the speed of the slowest RAM module.
The difference between the two types of DDR3 is in their supported voltages. Normal DDR3 requires 1,5 Volt, whereas DDR3L (L for Load reduced) also supports 1,35 Volt. This reduction in voltage results in a slightly lower power consumption. However, this reduction is so small, that the difference in battery life caused by using load reduced RAM even in laptops is hardly noticeable. It only makes a difference in data centers with hundreds of computers, each with up to 32 memory modules.
Even though the power consumption difference is tiny, you have to watch out for compatibility. Systems, which only support normal DDR3 usually, work with DDR3L, too, because it also supports 1,5 Volt. But there are computers, especially laptops, which only support DDR3L. Normal DDR3 might work here, however this is not guaranteed and might come with some stability issues. So, if you are not sure, which type of DDR3 your system needs, it is better to buy the load reduced variant or consult an expert.
The maximum amount of RAM your notebook supports depends on multiple factors:
You can use the following tools to see what RAM your Notebook needs:
AIDA (Download: www.lavalys.com)
CPUZ (Downlaod: www.cpu-z.de)
SIW (System Information for Windows) (Download from www.heise.de)
HWiNFO (Direct download here)
Alternatively, you can remove the currently installed RAM and read the necessary specifications from the labels on them. Should there be no label or should you not be able to recognize the type of RAM needed. You can still use the tools listed above or consult a specialist.