SD and SDHC are known to be two different types of memory cards. A lot of people can become confused between the two mainly because their sizes are similar to each other. You will know if it is SDHC if it goes beyond 4GB.
This means that if you have an SD card that is 4GB to 32GB, you can already expect that it will be considered as SDHC. Take note that aside from the storage capacity, you can also expect that there will be differences when it comes to their compatibility.
SDHC is expected to hold more data but they are not compatible with all devices. This is something that you need to know ahead of time.