If you're referring to an investigation in the context of a divorce, it typically involves gathering evidence or information to support claims during the divorce proceedings. Here are the common reasons and methods involved:

### Common Reasons for Divorce Investigations
1. **Infidelity**: Suspecting a spouse of cheating.
2. **Hidden Assets**: Believing that a spouse is concealing financial resources to avoid fair division of assets.
3. **Child Custody Issues**: Investigating parenting behaviors that may impact custody decisions.
4. **Substance Abuse**: Evidence of drug or alcohol abuse affecting the family.
5. **Lifestyle Claims**: Verifying the other party's claims about their lifestyle, income, or behavior.

### Methods Used
1. **Private Investigators (PIs)**:
- Surveillance (e.g., tracking movements or observing behaviors).
- Collecting photographic or video evidence.
- Conducting background checks.
2. **Digital Evidence**:
- Examining social media for incriminating posts.
- Checking email and phone records (ensure legality—court approval may be required).
3. **Financial Investigations**:
- Reviewing bank statements, credit card bills, and tax returns.
- Identifying undisclosed accounts or properties.
4. **Witness Interviews**:
- Friends, family, or coworkers may provide relevant insights.
5. **Legal Subpoenas**:
- Obtaining documents or evidence directly through court orders.

### Legal and Ethical Considerations
- **Consent**: Ensure investigations do not violate privacy laws.
- **Court Admissibility**: Evidence must be legally obtained to be used in court.
- **Professional Help**: Engage licensed professionals familiar with local regulations.

If you're considering a divorce investigation or need advice, feel free to elaborate on the situation, and I can provide tailored guidance.