Here are a few options for a WordPress post_tag description, keeping in mind practicality and SEO:

**Option 1 (Concise & Clear):**

> **繁體中文:** 了解ETF (交易所買賣基金) 的世界！ 掌握ETF入門知識，助你開始投資旅程。

* **Translation:** Understand the world of ETFs (Exchange Traded Funds)! Grasp basic ETF knowledge to help you start your investment journey.
* **Why it’s good:** Direct, uses clear keywords (ETF, 入門), emphasizes benefit.

**Option 2 (Slightly More Informative):**

> **繁體中文:** ETF入門：簡單瞭解ETF是什麼，如何買賣，挑選ETF的關鍵，以及開始投資的第一步。

* **Translation:** ETF Introduction: A simple understanding of what ETFs are, how to buy and sell, key factors in choosing ETFs, and the first steps to start investing.
* **Why it’s good:** Provides a bit more detail about what the content covers.

**Option 3 (Emphasizing Learning):**

> **繁體中文:** ETF入門指南：輕鬆學習ETF投資，從基礎知識到策略分析，一步步成為ETF投資高手。

* **Translation:** ETF Introduction Guide: Easily learn ETF investment, from basic knowledge to strategy analysis, step by step to become an ETF investment expert.
* **Why it’s good:** Appeals to the desire for improvement (expert) and implies a learning journey.

**Option 4 (Focus on Beginners):**

> **繁體中文:** 專為新手準備的ETF入門，深入淺出地講解ETF投資，讓你輕鬆掌握投資技巧，開啟財務自由之路。

* **Translation:** ETF Introduction prepared specifically for beginners, explaining ETF investment in an easy-to-understand way, allowing you to easily master investment techniques and start the path to financial freedom.
* **Why it’s good:** Good for targeting a specific audience, uses attractive keywords like “財務自由” (financial freedom).

**How to apply it in WordPress:**

1. **Navigate to “Tags” or “標籤”** in your WordPress dashboard (usually under “Posts” or “文章”).
2. **Find the “ETF入門” tag.** If it doesn’t exist, create it.
3. **Look for the “Description” field** (it’s often below the tag name and slug fields).
4. **Paste one of the descriptions** (or a variation) into the description field.
5. **Save the tag** (usually by clicking “Update” or similar button).

**Important Considerations:**

* **SEO Keywords:** The descriptions should organically include the key words “ETF” and “入門” (introduction).
* **Target Audience:** Consider who you’re writing for (beginners, experienced investors, etc.) and tailor the language accordingly.
* **Call to Action (Optional):** You *could* add a gentle call to action (e.g., “立即查看相關文章” – “Check out related articles now”) but it’s not essential for every tag.
* **Character Limit:** Be mindful of any character limits your WordPress theme or SEO plugin might impose on tag descriptions.

Choose the description that best fits the overall tone and purpose of your blog. Good luck!