In contrast to sin-offerings, which atone for unintentional sins, the guilt-offering can atone for certain intentional sins. Female goats or sheep can be used as personal sin-offerings, whereas only male sheep are used for guilt-offerings.
Male and Female Repentance
שְׂעִירַת עִזִּים תְּמִימָה נְקֵבָה וגו': (ויקרא ד:כח)
[G‑d told Moses that an individual’s sin-offering can be brought from] an unblemished female goat [or sheep]. Leviticus 4:28

There are two basic explanations of how sacrifices atone:

We should imagine that everything being done to the animal is being done to us. The sacrifice thus jolts us out of our negative ways.

The animal personifies our animal instincts, which led to the misdeed, in contrast to our Divine soul, which did not participate in the misdeed. The sacrifice stirs our Divine soul, inspiring us to serve G‑d better than we did previously.

The first explanation is harsher than the second, and is therefore appropriate for more severe misdeeds. Therefore, the guilt-offering, which can atone for deliberate misdeeds, is brought from male animals, suggesting the “male” meditation necessary to shake a person free from deliberate misbehavior. The second, gentler, more “female” meditation is more appropriate for unintentional misdeeds; therefore, the sin-offering, which atones for such misdeeds, is brought from female animals.

When we feel estranged from G‑d and seek to draw closer to Him, we need to evaluate the cause of our estrangement. We can then meditate on our relationship with G‑d in the way appropriate to our situation and take the appropriate corrective action.1