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Found in vs planned for
Accepted answer
"Planned for" allows to select an iteration in a development time line, which is marked as "A release is planned for this iteration". The meaning of which is that the work is planned to be done and finished within the selected iteration. This information is used for planning.
"Found In" allows to select a Release that is specified in the project area to specify in which release the issue came up, so that a developer knows what context to set up. A Release can be an artificial thing such as 6.0.3M1 or generated from a real build e.g. the one that shipped.