A method for performing a concept-based search on digital data, the method, comprising: receiving from a first user a first search query; providing a first set of one or more search results including identification of a plurality of content items responsive to the first search query; forming a concept hierarchy based at least in part on one or more concepts, each concept from the one or more concepts being based on a meaning extracted from at least one content item from the plurality of content items and comprising at least one of: a word, an image, a number, a symbol, an idea, a meaning in a context, or a relationship between two or more of a word, an image, a number, a symbol, a document, or a data set; revising, in response to user input, at least a portion of the concept hierarchy, the revising including at least one of: deleting a first user-selected concept from the concept hierarchy; inserting a first user-defined concept into the concept hierarchy; and revising a relationship between a second user-selected concept and a third user-selected concept in the concept hierarchy; forming a second search query based at least in part on one or more of: the first user-defined concept; the first user-selected concept if not previously deleted; the second user-selected concept; the third user-selected concept; and a fourth user-selected concept from the concept hierarchy; providing a second set of one or more search results responsive to the second search query; storing analysis created by the first user and received from the first user, the analysis being based on at least one of the concept hierarchy, and at least a portion of the second set of one or more search results; and providing to a second user: at least a portion of the second set of one or more search results; and the analysis; wherein at least one of the receiving, providing a first set, forming a concept hierarchy, revising, forming a second search query, providing a second set, storing and providing to a second user is performed at a processor. receiving from a first user a first search query; providing a first set of one or more search results including identification of a plurality of content items responsive to the first search query; forming a concept hierarchy based at least in part on one or more concepts, each concept from the one or more concepts being based on a meaning extracted from at least one content item from the plurality of content items and comprising at least one of: a word, an image, a number, a symbol, an idea, a meaning in a context, or a relationship between two or more of a word, an image, a number, a symbol, a document, or a data set; a word, an image, a number, a symbol, an idea, a meaning in a context, or a relationship between two or more of a word, an image, a number, a symbol, a document, or a data set; revising, in response to user input, at least a portion of the concept hierarchy, the revising including at least one of: deleting a first user-selected concept from the concept hierarchy; inserting a first user-defined concept into the concept hierarchy; and revising a relationship between a second user-selected concept and a third user-selected concept in the concept hierarchy; deleting a first user-selected concept from the concept hierarchy; inserting a first user-defined concept into the concept hierarchy; and revising a relationship between a second user-selected concept and a third user-selected concept in the concept hierarchy; forming a second search query based at least in part on one or more of: the first user-defined concept; the first user-selected concept if not previously deleted; the second user-selected concept; the third user-selected concept; and a fourth user-selected concept from the concept hierarchy; the first user-defined concept; the first user-selected concept if not previously deleted; the second user-selected concept; the third user-selected concept; and a fourth user-selected concept from the concept hierarchy; providing a second set of one or more search results responsive to the second search query; storing analysis created by the first user and received from the first user, the analysis being based on at least one of the concept hierarchy, and at least a portion of the second set of one or more search results; and providing to a second user: at least a portion of the second set of one or more search results; and the analysis;