The H-index is a way of calculating a researcher's scholarly impact based on the number of papers they have published and the number of times those papers have been cited. Your h-index will vary depending on what tool you use to calculate it, because tools have differing rules around what publications they include in the count.
The Citation Report allows you to create a report of a researcher's citations in Web of Science, as well as an h-index based on those citations.
Keep in mind that for this report, Web of Science only uses data from journals indexed in that database — not all disciplines are equally covered. It is particularly strong in the sciences and most social sciences.
Your citation count and h-index appears on a profile that you create in Google Scholar.