There is no single “best probiotic.” The right choice depends on the goal: constipation, diarrhea, bloating, post-antibiotic recovery, or IBS-like symptoms are different scenarios with different evidence. Strain-level detail matters—“Lactobacillus” on a label is not enough; the species/strain identifier and dose (CFU) should be clear. Outcomes also vary by person because baseline microbiota, diet, stress/sleep, and medications influence response. Practical selection criteria include: (1) human studies for the intended outcome, (2) an adequate dose and viability through shelf life, and (3) reputable manufacturing and transparent labeling. In immunocompromised patients or those with high-risk clinical situations, probiotic use should be assessed more cautiously. For long-term “gut resilience,” probiotics work best as part of a broader plan: fiber-rich foods, consistent sleep, stress management, and—when appropriate—prebiotic or synbiotic approaches.