What does 5000k or 3000k mean?
When you see these numbers it relates to color temperature. The designation of 5000k is close to daylight white (about 12:00 noon). In reality, this is natural light in contrast to 3000k which is a warmer white. 3000k has a yellow tint to it and is close to incandescent bulbs that are in homes. Many people find warm white to be more natural, but this could be because these bulbs are so prevalent in many homes.
What is a PAR30 & PAR38?
Many homes have recessed lighting which use Par 30 or Par 38 bulbs. PAR is the enclosure type. The bulb shape is classified as PAR which stands for parabolic reflector. The additional number (ie 30 or 38) is the maximum diameter of the bulb. To get the size of the diameter in inches, you just divide the number by 8. In this case a PAR38 is equal to 38 divided by 8 which equals 4-3/4 inches. Many LED bulbs have a PAR comparison but they cannot be PARs because LED bulbs don't have parabolic reflectors.
What bulb type is a standard bulb?
A standard bulb has three designations. The first is the enclosure type which is A (Standard). The second is the diameter such as 18 or 18 eighths of an inch (2-2/8 inches diameter). The third is the base. There are many bases, but for this case we will use a medium base (or E26).