How they differ
In the gym the load comes from weights and repetitions, and it is satisfying to watch the numbers grow. In yoga the main equipment is your own body, and you work with holding poses, balance and breath. It is a different kind of effort, neither better nor worse.
The atmosphere differs too. In the gym people usually train on their own, while in yoga a teacher leads and the group moves together. If you like cues and structure that is a plus; if you want full freedom, the gym is easier.
What yoga trains
Yoga builds joint mobility, steadiness, strength in the trunk and legs, and the skill of relaxing. Poses such as plank and warrior II load the muscles well, and in dynamic styles the heart rate climbs noticeably.
The load depends on the style. Hatha and yin are calmer; vinyasa and power yoga ask for more. In class you will often hear about bandha, a gentle engagement of the trunk and pelvis muscles that helps you hold a pose.
Where the gym is stronger
The gym wins where you need heavy weights, exact dosing and quick strength gains. If your aim is building muscle or preparing for a strength sport, a programme with a coach is more direct.
Even there mobility matters: it helps you perform exercises with good technique. Yoga can be a useful addition.
Combining them in one week
A simple plan is two strength sessions at the gym plus one or two yoga classes, for example on a rest day or in the evening. Do not put a dynamic vinyasa straight after heavy legs, while a gentle practice after the gym is fine.
The guide on how often to practise has more on rhythm. If you are choosing a style, open the guide on how to choose a yoga style.
What to expect in the first weeks
In the gym progress shows up as weights and repetitions, so motivation often arrives fast. Changes in yoga are quieter: first it is easier to breathe in a pose, then balance steadies, and later folds go a little deeper.
Do not compare the two scales directly. It helps to note in a notebook how you slept, how your back feels and how many seconds you hold tree pose on one leg. Notes like that help you see your progress even when it is not visible.
In both places gradual progress and good technique matter. A trainer at the gym and a teacher in class can help you avoid unnecessary risks, especially if you have an injury: mention it before you start.
When to pick yoga and when the gym
If you want mobility, calm and a new way of moving, start with yoga. If your aim is to build strength quickly or to prepare for sport, add the gym. If you want a bit of everything, combine them in one week.
Both are good as long as you return to them without forcing yourself. Choose what leaves you pleasantly tired rather than exhausted, and review the choice every two or three months.
Choosing for yourself
Ask yourself three questions. What do I want: strength, flexibility, calm or a bit of everything? How much time do I have? What will I enjoy doing for months? Try each for a couple of sessions and compare how you feel, and if you have any particular health needs, check with a teacher beforehand.