Before us is Mishnah 7 in the first chapter of Maseches Moed Katan, which deals with the laws of marriage and of a woman preparing her cosmetics on Chol HaMoed.
The Prohibition of Marrying on the Festival:
The Mishnah rules: "Ein nos'in nashim ba'mo'ed" - one may not marry a woman on Chol HaMoed, and it spells this out:
"Lo besulos" - not a woman who was never married before.
"V'lo almanos" - and not even a woman who was already married once.
"V'lo m'yabmin" - even the mitzvah of yibum, marrying one's brother's widow, is not performed on the festival.
The Reason for the Prohibition:
The Mishnah gives the reason: "V'nisa simchah hi lo" - marriage is a joy in its own right, and from here emerge two reasons for the prohibition:
It is a halachah that we do not mix one joy with another, and one may not combine two separate celebrations.
There is a concern that a person will set aside the joy of the festival and become occupied with the joy of his new wife.
What Is Permitted on the Festival:
"Aval machzir es gerushaso" - one who was married to a woman, divorced her, and now marries her again - the very same couple - may do so even on Chol HaMoed.
"V'osah ishah tachshiteha ba'mo'ed" - a woman is permitted to adorn herself and apply her full range of cosmetics on Chol HaMoed.
The View of Rabbi Yehudah:
Rabbi Yehudah disagrees and says: "Lo tasud" - she may not use lime, a kind of chemical paste for removing hair. And his reason: "V'nivul hu" - as long as the lime paste is resting on her body it causes her pain and she does not look attractive, and therefore this should not be done on Chol HaMoed.
The Gemara, however, explains that even Rabbi Yehudah agrees that if the lime is due to come off during Chol HaMoed, so that its purpose is achieved within the festival itself, this is a joy for her and it is permitted. For not only is the preparation done on Chol HaMoed, but the result too is hers to enjoy during the festival - and in such a case it is permitted even according to Rabbi Yehudah.
In summary: In this Mishnah we learned that one may not marry on the festival - not a woman marrying for the first time, not a widow, and not even through yibum - because we do not mix one joy with another, and because of the concern that a person will be distracted from the joy of the festival. But one may remarry his own divorcee, and a woman may prepare her cosmetics on the festival. Rabbi Yehudah forbids lime because of the unattractive appearance it causes, yet he agrees regarding lime that comes off within the festival, in which case even he permits it.