An "in-kind" contribution for political purposes is a donation of materials or something of value to a campaign other than money.
A leading example of this type of contribution is set forth at 11 CFR 109.23:
§ 109.23 Dissemination, distribution, or republication of candidate campaign materials
(a) General rule. The financing of the dissemination, distribution, or republication, in whole or in part, of any broadcast or any written, graphic, or other form of campaign materials prepared by the candidate, the candidate's authorized committee, or an agent of either of the foregoing shall be considered a contribution for the purposes of contribution limitations and reporting responsibilities of the person making the expenditure. The candidate who prepared the campaign material does not receive or accept an in-kind contribution, and is not required to report an expenditure, unless the dissemination, distribution, or republication of campaign materials is a coordinated communication under 11 CFR 109.21 or a party coordinated communication under 11 CFR 109.37.
(b) Exceptions. The following uses of campaign materials do not constitute a contribution to the candidate who originally prepared the materials:
(1) The campaign material is disseminated, distributed, or republished by the candidate or the candidate's authorized committee who prepared that material;
(2) The campaign material is incorporated into a communication that advocates the defeat of the candidate or party that prepared the material;
(3) The campaign material is disseminated, distributed, or republished in a news story, commentary, or editorial exempted under 11 CFR 100.73 or 11 CFR 100.132;
(4) The campaign material used consists of a brief quote of materials that demonstrate a candidate's position as part of a person's expression of its own views; or
(5) A national political party committee or a State or subordinate political party committee pays for such dissemination, distribution, or republication of campaign materials using coordinated party expenditure authority under 11 CFR 109.32.